1. Field of the Invention
The subject matter of the present invention consists of a specially designed multilumen electrocatheter which, for its configuration and materials, can be localized and driven close to an arrhythmogenic target in connection with a magnetocardioagraphic mapping and localization technique. The catheter can also be used as a guide for ablation and/or biopsy devices, for fluid infusion and to apply suction.
2. Description of the Prior Art
During the last twenty years, the electrogenetic mechanism of cardiac arrhythmias has been widely investigated the clinical level by combining direct recording of endocardial electrograms and programmable electrical stimulation of the heart.
For both endocardial recording and pacing, commercially available electrocatheters are usually reliable, provided that a recording bandwidth of 30/50-1000 Hz is used. In particular high pass filters are mandatory to obtain stable recordings and avoid offset phenomena due to biological low frequency components (such as respiration) or to polarization of the electrodes during recording and pacing. Filtered signals are reliable for timing local endocardial activation, but inadequate for studying the of transient variation of specific electrophysiological parameters. On the contrary, the recording of monophasic action potential (MAP), a signal which must be typically recorded in open bandwidth (DC to 1 KHz), is gaining a growing interest for the beat-to-beat study of cardiac repolarization and of diastolic arrhythmogenic phenomena under different pathophysiological conditions. At present for MAP recordings, in order to the polarization phenomena, electrocatheters with Ag/AgCl electrodes are used which however polarize if used for pacing. It is evident therefore that it would be impossible to employ the same electrocatheter for monophasic action potential recording and endocardial pacing. On the other hand, MAP recordings have to be carried out in close proximity to the arrhythmogenic areas when diastolic phenomena, such as afterpotentials, have to be identified. A method is needed therefore to drive a mapping catheter, as well as biopsy or ablation devices, right onto the arrhythmogenic zone.
Catheter positioning and localization are usually carried out under fluoroscopic control, with a spatial resolution which is sufficient for routine electrophysiological evaluations, but sometimes inadequate for an accurate three-dimensional localization of arrhythmogenic foci, which is the prerequisite for successful surgical or catheter ablation of arrhythmias. The precision of catheter positioning can be moderately improved by measuring the "local activation time" on the electrograms recorded by the catheter in respect of a fixed reference lead, and taking into account the morphology of the signals.
In order to improve the pre-surgery localization of arrhythmogenic structures, different intracardiac mapping methods have been developed, which imply the use of multielectrode catheters. The spatial localization accuracy of such invasive methods has not been precisely quantified so far. Its average uncertainty is estimated in the order of 1.5-2 cm in the three dimensions.
In patients who undergo open chest surgical ablation of arrhythmias, it is usually possible to verify the preoperative localization accuracy by intraoperative epicardial mapping. On the contrary when catheter ablation is the procedure chosen, the success is only dependent on:
(a) The accuracy of catheter mapping to localize the arrhythmogenic area. PA1 (b) The capability to drive the ablation catheter right within (or as close as possible to) the target arrhythmogenic tissue. PA1 (1) biomagnetic localization of the tip of the catheter, PA1 (2) monophasic action potential and standard electrograms recording, and PA1 (3) endocardial pacing. PA1 (A) Conventional (filtered) intracardiac mapping; PA1 (B) Intracardiac mapping of monophasic action potentials. PA1 (C) Calibration of biomagnetic systems for accuracy of cardiac sources localization; PA1 (D) Biomagnetic localization of the catheter tip position with respect to the site of origin of cardiac arrhythmias, previously localized by magnetocardiographic mapping; and PA1 (E) An integrated system for biomagnetically driven intracardiac catheter ablation of arrhythmogenic tissue and/or endomyocardial biopsy.
The latter point is obviously more critical when extremely focused ablation energies (i.e. laser, radiofrequency or thermal ablation) are chosen, which determine lesion of only a few millimeters. Catheter positioning reproducibility is extremely important taking into account that in some cases multiple sessions are needed for complete ablation of the arrhythmogenic tissue.